Frostless Heat Exchanger Using Air–Silicone Oil Direct Heat Exchange

Abstract

A frost-free heat exchanger using silicone oil is developed in this study. This heat exchanger directly exchanges heat between air and silicone oil. First, an orthogonal flow heat exchanger is constructed, where the flow of air is orthogonal to that of silicone oil. In this heat exchanger, oil is scattered downstream because of air flow. Piano wires are placed in an oil column to prevent oil scattering. Oil flows along the wires, and the oil flow is stabilized successfully. However, air flow causes the oil surface to ripple and the surface of the piano wires to be exposed partially to the air. Ice accumulates at the exposed surface and eventually obstructs the oil outlet. Ice accumulation is reduced slightly by applying a hydrophobic coating to the piano wires. However, the coating does not prevent outlet obstruction. Next, we improve the heat exchanger as the oil flows in the same direction as the air. This improvement allows us to remove the piano wires. The developed heat exchanger can be operated without frost formation for 1 h where, during the operation, the pressure loss of the heat exchanger does not increase.